This intention relates to a method and an apparatus for compacting molding sand.
In one conventional method of compacting molding sand that has been charged into a mold space defined by a pattern plate and a flask, means for compacting the molding sand and the pattern plate are moved relative to each other. In this method a molding machine requires a large hydraulic cylinder for vertically moving the pattern plate, and hence has a high profile. This produces a problem in that, for example, a pit must be provided in a floor when the machine is installed on it. Further, separating a produced sandmold from the pattern plate cannot be done stably. Thus it is difficult to make smaller the draft of the sandmold. A great draft would make a sandmold heavy. Certainly, this is not preferable. Further, even when the properties of the molding sand are changed, the conditions for the compaction cannot be readily changed.
This invention has been conceived in view of the drawbacks discussed above. It is a purpose of the invention to provide a method that does not require a large hydraulic cylinder for vertically moving a pattern plate, which requires a pit, and that can compact almost all of the molding sand, which has been charged into a mold space defined by a flask and a pattern plate, to a desired degree.
It is a further purpose of the invention to provide a method of compacting molding sand wherein a small draft can be provided for a sandmold.
It is a further purpose of the invention to provide a method of compacting molding sand wherein a sandmold that has a uniform height is produced by the best compacting conditions even if the properties of the molding sand change.
It is a further purpose of the invention to provide a molding machine to implement the method of the invention.
To the above end, the method of the present invention is a method for compacting molding sand in a mold space defined by a pattern plate, which is fixed in a horizontal position when the molding sand is compacted, a leveling frame disposed for vertical sliding movement around the outer periphery of the pattern plate, a frame member disposed for vertical movement above the leveling frame, and a filling frame disposed for vertical movement above the frame member, comprising the steps of: feeding molding sand into the mold space; primarily compacting the molding sand in the mold space from above by compacting means while at least the leveling frame is being set so that it can be lowered; and secondarily compacting from above, by the compacting means, the molding sand in the mold space while the leveling frame, the frame member, and the filling frame are set so that they can be lowered.
In one aspect of the method of the invention, the method may include the step of adjusting the volume of the mold space before the step of feeding the molding sand into the mold space takes place.
In this invention the term xe2x80x9cframe memberxe2x80x9d denotes a flask when a mold to be produced is a mold held in a flask, or a molding frame when a mold to be produced is a flaskless mold. Further, a xe2x80x9cmoldxe2x80x9d to be produced includes a mold held in a flask and a flaskless mold, which has been removed from a molding frame after it had been solidified in the molding frame. Further, the pressure for secondarily compacting the molding sand may be equal to that for primarily compacting the molding sand. However, a higher pressure in secondary compacting than in primary compacting would enhance the effect of the invention. Further, in this invention the compacting means may be any type of a single member to compact molding sand, a plurality of members to compact molding sand, such members being provided with flexible sheets on which pressurized air is applied, etc. Further, after the step of adjusting the volume of the mold space, the molding sand may be fed into the mold space. By this, the conditions for the compaction can be readily determined in accordance with the change in the molding sand